Soundcard interfaces are used primarily to isolate the PC from the transceiver. This reduces the risk of a ground loop, preventing hum and noise on the modulation. Besides the pure isolation of AF signals some of these devices offer more functions like level adjustment, PTT control, CW keying and a CAT interface as well.
The more recent developments use the USB interface from the PC instead of the serial port for control functions.

SB-2000Mk2 USB Transceiver Interface

Yaesu SCU-17 CAT- and sound card interface with built-in sound card

The Yaesu SCU-17 is an interface to run with digital operating modes for almost all current Yaesu transceivers. The SCU-17 works as a USB sound card, therefore only one USB cable is required between interface and computer. The interface isolates all signals galvanically to avoid potential ground loops. In doing so the audio-in and audio-out, PTT, FSK and CAT signals are transmitted. The key signals are seperated by Opto-isolators, the audio signals by coupling transformers.

Overview microHAM Sound card interfaces and station controllers

microKEYER-2R/2R+
Universal controller for two radios. The microHAM device with the most fucntions! Ideal for contest operation with two radios at the same time (SO2R) or for everybody who wishes to control two (even different) radios at the same time. Supports all modes: Phone, CW, digital modes. The microKEYER-2R+ has an internal sound card integrated, the microKEYER-2R uses the built-in sound card of your computer.
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microKEYER-II
Controller with internal USB sound card. The microKEYER-II supports the flexible selection of the audio source (microphone, sound card) depending on mode. Ideal for users who wish to use all modes including phone, CW or digital modes, and who wish to have a separate high level sound card for digital modes. Useful for day to day operations as well for the contest, all modes.
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USB-II
Controller which supports all basic functions like CAT, PTT and CW keying as well as audio from the computer sound card. Like all microHAM interfaces of course with galvanic isolation of all signals. Excellent price/performance ratio, regardless if used during the contest or for the daily operations with a computer log at home.
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USB-III

Like USB-II, plus built-in sound card. Only one USB cable from interface to your computer, better sound quality. The computer soundcard remains free for other purposes, no more swaping cables when using the radio.
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Comparision microHAM Interfaces

microKEYER-2R+

microKEYER-2R

microKEYER-2

microKEYER

Digikeyer

USB-2

USB connection

Yes

Yes

Yes

Yes

Yes

Yes

Galvanic isolation of all connections

Yes

Yes

Yes

Yes

Yes

Yes

CAT/CI-V Interface

Yes

Yes

Yes

Yes

Yes

Yes

PTT & CW keying

Yes

Yes

Yes

Yes

Yes

Yes

True FSK keying

Yes

Yes

Yes

Yes

Yes

Yes *

Connector for opt. PS/2 keyboard

Yes

Yes

Yes

Yes

Yes

No

CW keying with WinKey chip

Yes

Yes

Yes

Yes

No

No

Audio source routing (micro/soundcard)

Yes

Yes

Yes

Yes

No

No

Supports two radios

Yes

Yes

No

No

No

No

Internal USB soundcard

Yes

No

Yes

No

Yes

No

Multifunction LC display

No

No

Yes

No

No

No

Required radio cable type

2x DB37-xxx

2x DB37-xxx

1x DB37-xxx

1x DB37-xxx

1x DB15-xxx

1x DB15-xxx

* The USB-2 interface supports FSK for example with the EXTFSK software by MMTTY (free).

RigBlaster Nomic
Basic interface which is useful for very affordable operations of an Echolink gateway or for portable uses. PTT keying with serial interface of the computer. No external power suppyl required.
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Other CAT interfaces

Besides the above mentioned sound and CAT interfaces we offer a few pure CAT interfaces, i.e. devices which allow only the control of the CAT functions by the computer.